Best “Bang for your buck” Engine?

[virus]

In answer to the original question. I think you cant got far wrong with the oilbooler suzuki lumps, leave the 6s alone but the GSX750F had more than enough grunt to get you around and a respectable MPG. The Bandit 12 moreso was a sufficiently torquey motor that still did respectable mpg for something of its CC.
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own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

[DJP]

So it's looking like a 600-700cc (ish) twin is the sweet spot.

I can well believe it. I did 12,000 miles on an MT07, in the real world it was as quick as my 1250 Bandit but averaged 60mpg over my ownership. And I didn't baby it.

The Honda NC is another obvious example, similar to the MT07 but capped at 6,000 (ish) rpm. And I'm told that the V-Strom and SV 650s have pretty decent economy too.
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Suzuki Bandit 1250
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